Testing device



July 15, 1941. w, B MARTlN 'i i 2,249,153

TESTING DEVICE Filed May 2, 1939 2 sheets-sheet .1

/NVEA/ron BY W. B. MART/N ATTORNEY July15, 1941. WE1/mmm 2,249,153

TESTING DEVICE Filed May 2, 1939 2 Sheets-Sheet 2 Afro/wmfL Patented `uly 15, 1941 UNITE TESTEN; DEVICE Wade B. Martin, Westwood,l N. J., assignor to American Telephone and Telegraph Company, a corporation of New York Application May 2, 1939, se1-ia1No.271,402

(ci. 17a-69) 3 Claims.

This invention relates to testing devices and particularly to means for testing communication circuits.

It is an object oi the invention to provide a low cost device of extreme exibility which will give an instantaneous and positive indication of a condition to be detected in a communication circuit. A further object is to pro-vide such a means in a form which will cause no disturbance in the circuits to which it is at any time connected and which will not interfere with normal service over such circuits.

Accordingly, a testing circuit of high impedance is provided including an indicating device of such high impedance and which requires for its operation so little current that its connection to a circuit will not interfere with normal operation. In practice this may take the form of a neon lamp circuit so proportioned that the lamp will flash at a given critical voltage.

A feature of the invention is a switchboard plug for cooperation with the spring jacks of a communication circuit switchboard, which plug is so constructed and arranged that upon insertion into a spring jack it will make electrical connections with the various elements of the jack without operating such elements inthe normal manner. Where a spring jack is arranged to break the continuity of a circuit by lifting a spring out of contact with another upon the insertion of a plug, the insertion of the plug described herein will fail to cause such an operation. In the form shown a feature of this invention is a plug provided with a flexible tip element which has a considerable range 'of movement and sufficient spring tension to make a rm Contact with the cooperating spring of a jack but insuicient tension to overcome the normal tension of such jack spring.

Another feature of the invention is a plug structure carrying certaincircuit elements and indicating means whereby a portable testing device of small dimensions is provided. Such a device may be inserted in a spring jack of a circuit suspected of operating in an unstandard manner and, without causing any electrical disturbance.fact as a detector of unstandard conditions.

By using a plurality of such plugs each inserted into the jack leading to a branch of a single communication circuit, the offending branch may be quickly identified. Y

The drawings consist of two sheets,-the rst containing Figs. 1, 2 and 3, each being a view of the plug partly Ain-section. In Figs. 1 and 2 the plug is shown as inserted in a spring jack, with its tip flexed, while in Fig. 3 the plug alone is shown and the tip is shown in its normal position. Fig, 4 shows the plug when used as a selfcontained testing device and when used as part of a testing device when connected to the remainder of the testing .circuit by a conductor leading from the circuit contained within the plug shell. In this figure three such plugs are shown in association with a communication circuit, the Whole forming a circuit diagram. Fig. 5 is a circuit diagram illustrating the invention and the manner of its use'when the whole of the testing circuit is external to the plug, that is,

when the plug does not form a self-containedV testing device.

In Fig. l a spring jack I is shown in sectional outline. A jack spring 2 is shown stilll in connection with a contact V3 insulated from the body of the jack I by an insulating bushing 4.

' ner diameter of the sleeve 5 and the insulating bushing 9 is of the order .of several times the diameter of the steel spring wire 'I the latter has a considerable range of movement. In fact, this range may be statedto be comparable to the outside diameter of the sleeve as is clearly indicated in the drawing.

An insulating cylinder or shell I0 is held to the sleeve 5 and is maintained in position by a screw Il, and forms ameans for handling the plug without making contact with any of its conducting elements and a protective housing for the apparatus forming the circuit associated therewith.

A pair of resistance elements I2 and I3 andVVA a glow lamp I4 are shown mounted within the shell I0 and certain connecting wires are shown though no attempt has been made to show the entire circuit arrangement. v

The added conductor is not connected to sleeve 5. The lamp resistance connection to the sleeve in Fig. 1 is removed and is connected to conductor I5.

Fig. 3 is a circuit arrangement which illustrates a line I'I entering a central oice generally shown by the broken line rectangle and leaving the central oce over the conductor I8. The circuit may be traced from the line I'I.

Fig. 2 shows another view of the plug only partly in section. This ligure illustrates the arrangement when a connection from the junction of resistance I3 and neon lamp I4 instead of being made to the sleeve 5 is made to a conductor I5, which is then connected to some other point as the tip of another plug as illustrated in Fig. 4, in association with jack 26.

Fig. 3 is another view of the plug. In this view the plug is not inserted in a spring jack and so the tip 8 and spring I are shown in their normal positions. Also in this view the plug is shown with two conductors 33 and 34 connected to the tip and sleeve respectively for connection to a testing circuit entirely external to the plug as shown also in Fig. 5.

Fig. 4 is a circuit diagram illustrating a line I7 entering a central oflice generally shown by the broken line rectangle and leaving the central oiiice over conductor I8. The circuit may be traced from the line I'I, through the repeater consisting of the two polarized relays I9 and 2i), the contacts of spring jack 2I, the contacts of spring jack 22, the contacts of spring jack 23 over a local loop to teletypewriter station 24, the contacts of spring jack 23, the contacts of spring jack 25, the contacts of spring jack 26, the repeater consisting of the two polarized relays 2'I and 28 to the line I8. A self-contained testing device as in Fig. l is plugged into jack 2| and jack 23 and another of the variety of Fig. 2 is plugged into the jack 26 with a connection made over conductor I5 to battery on the tip of jack 29. It will be noted in each case that the steel spring 'I is bent so that the tip piece 8 makes contact with the tip spring of the jack without lifting such tip spring oi its contact so. that, therefore, the mechanical positions of the jack springs have not been disturbed.

In the case of jack 2I the electrical connections form a high impedance bridge from the line to battery comprising a connection from the line, the tip spring of jack 2|, the tip piece 8 of the test plug, the spring 1, the resistance I 2 and then in parallel with each other, the resistance I3 and the glow lamp I4 to the sleeve 5 of the plug, the sleeve of the jack 2I to battery. Since the impedance of this circuit is very high the signals over the line will not be disturbed.

By way of example, the various batteries may be 130 volts plus or minus, the resistance I2 may be 1,000,000 ohms (1 megohrn) resistance I3 may be 750,000 ohms and the lamp I 4 may be a switchboard type glow lamp. With these values the lamp will not flash when the terminal voltage is as low as 130 volts but will begin glowing at about 160 volts and will reach full brilliance at 260 volts at which the current drain is only twotenths of a milliampere. These values may be modified over a wide range in accordance with the character of the tests to be made.

In the present instance the relays in Fig. 4 are all shown in their marking contacts and it is assumed that the lines I'l and I8 and the loop to station 24 are in a closed or marking condition. Under these conditions the voltage across the tip 8 and sleeve 5 of the plug inserted in jack 2I is very low depending on the drop from the tip of jack 2I to the marking` contact of relay I9. The lamp I4 will not glow under these conditions. Should the line I 1, however, go` to. spacing, as

when the line is opened, then relay I9 will go to spacing and the lamp I4 and its potentiometer circuit will be subjected to something approaching 2'60 volts, the addition of the plus battery on the spring contact of relay I9 and the minus battery on the sleeve of jack 2I. Lamp I4 will glow under these conditions and thus indicate an Open condition in line I1. Open conditions of extremely short duration, known as hits may be detected with this testing device. Should the line be opened in the other direction, say at jack 22 or in the station 23, the lamp I4 will not re- 'spond since the voltage across the jack 2'I then becomes zero, there being no drop to the tongue of relay I9. The testing device in jack 2| therefore, is a faithful indicator of the condition of line I1.

Likewise, the testing device in jack 26 is a faithful indicator of the condition of line I8 though the potentials are reversed at this point. This also illustrates the arrangement when the Sleeve of the jack has no battery connection. In this case the arrangement of Fig. 2 is used and Aa separate wire I5 is connected to a battery connection through jack 29.

In the case of loop jack 23 a self-contained testing device as in Fig. 1 is used and the testing circuit is connected to the loop conductors. Thus when the circuit through station 24 is opened, the lamp I4 will glow and only then.

With the'three testing devices in the three jacks 2|, 23 and 26 an observer will quickly observe which branch of the line or the loop to station 24 is open or being opened or closed. The testing devices inserted in the jacks do not mechanically disturb the contact arrangements or electrically disturb the circuit arrangements.

In Fig. 5 a line is shown entering a central office and terminating in a battery connection to the sleeve of loop jack 3|. The loop jack 3| gives access to local station 32 and the testing device inserted therein will give a faithful indication ofY the condition of the loop and station 32 in the same manner as the testing device inserted in jack 23. This illustrates the use of the plug in a simple jack such as jack 3| where there are no auxiliary contacts and here the potentiometer circuit may be connected to an ordinary plug since movement of the jack springs need not be avoided, but the circuit arrangement is the same. As actually illustrated the plug of Fig. 3 is shown with a testing circuit Which may be separately mounted at a distance as indicated by the broken lines betweenv such testing circuit and the plug itself. Thus if the loop or station 32 goes to spacing or becomes opened the full potential of the battery connected to the sleeve of jack 3I is added to the potential onv the marking contact of relay I 6 to cause lamp I 4 to glow.

What is claimed is:

Y 1. A test plug for communication switchboards comprising a conducting sleeve member, an insulating shell surrounding a portion of said sleeve member, a gaseous conduction lamp mounted within said sleeve member, a iiexible conducting tip member insulatingly supported by said sleeve member, and impedance elements lconnecting said lamp to at least one of said conducting members.

- 2. A plug for insertion intoV a spring jack comprising a cylindrical shell of conducting material and a concentrically arranged steel spring wire carrying at its outer extremity and beyond the end of said cylindrical shell a contact member of conducting material, the inner diameter Sleeve members insulated from each other, said of said cylindrical shell being of the order of tip member comprising a resiliently mounted several times the diameter of said steel spring contact piece having a range of movement com- Wire. parable to the outside diameter of said sleeve 3. A plug for insertion into a spring jack 5 member. comprising concentrically arranged tip and WADE B. MARTIN. y. 

